The long term evolution (LTE) system has two frame structures. The frame structure Type 1 is applicable to frequency division duplex (FDD) and frequency division half-duplex. Each radio frame has a length of 10 ms, and consists of 20 slots, each of which has a length of 0.5 ms and which are numbered from 0 to 19. Here, one subframe consists of two continuous slots, e.g., subframe i consists of two continuous slots 2i and 2i+1.
The frame structure Type 2 is applicable to time division duplex (TDD). One radio frame has a length of 10 ms, and consists of two half-frames each having a length of 5 ms. One half-frame consists of 5 subframes each having a length of 1 ms. The special subframes consist of a downlink special subframe (DwPTS), a guard period (GP), and an uplink special subframe (UpPTS), and have a total length of 1 ms. Each subframe i consists of two slots 2i and 2i+1 each having a length of 0.5 ms (15360×Ts).
In the above-mentioned two frame structures, for a normal cyclic prefix (normal CP), one slot contains 7 symbols each having a length of 66.7 us, wherein the length of the CP in the first symbol is 5.21 us, and the length of the CP in each of the rest 6 symbols is 4.69 us; for an extended cyclic prefix (extended CP), one slot contains 6 symbols each having a CP length of 16.67 us. The special subframe configuration is shown in Table 1, wherein 30720·Ts=1 ms.
TABLE 1Special Subframe Configuration.Downlink using normalDownlink using extendedcyclic prefixcyclic prefixUpPTSUpPTSSpecialUplink usingUplink usingUplink usingUplink usingSubframenormalextendednormalextendedConfigurationDwPTScyclic prefixcyclic prefixDwPTScyclic prefixcyclic prefix0 6592 · TS2192 · TS2560 · TS 7680 · TS2192 · TS2560 · TS119760 · TS20480 · TS221952 · TS23040 · TS324144 · TS25600 · TS426336 · TS 7680 · TS4384 · TS5120 · TS5 6592 · TS4384 · TS5120 · TS20480 · TS619760 · TS23040 · TS721952 · TS———824144 · TS———
One resource element (RE) is an orthogonal frequency division multiplexing (OFDM) symbol in a time domain, and is a sub-carrier in a frequency domain. One slot contains NsymbDL OFDM symbols. One resource block (RB) consists of NsymbDL×NscRB resource elements, and is one slot in a time domain and 180 kHz in a frequency domain. When the subframe cyclic prefix is a normal cyclic prefix, one resource block is shown in FIG. 1. The same frequency domain in one subframe corresponds to a pair of resource blocks (also referred to as RB-pair).
Three downlink physical control channels are defined in LTE as follows: physical control format indicator channel (PCFICH), physical hybrid automatic retransmission request indicator channel (PHICH), and physical downlink control channel (PDCCH). The physical control format Indicator channel carries information that indicates the time domain size of the downlink control region in the subframe.
The physical downlink control channel (PDCCH) is mapped to physical resources, with a control channel element (CCE) as a unit. One CCE has a size of 9 resource element groups (REGs), i.e., 36 resource elements. The PDCCH has four aggregation levels which respectively represent that one PDCCH occupies 1, 2, 4 and 8 CCEs, called as aggregation level 1, aggregation level 2, aggregation level 4 and aggregation level 8; correspondingly, the 4 aggregation levels correspond to four formats of PDCCH, that is, the aggregation level represents the size of the physical resources occupied by the physical downlink control channel. In addition, the search space of the physical downlink control channel of user equipment is partitioned into a common search space and a UE-specific search space.
In the LTE system Release (R) 8/9, a common reference signal (CRS) is designed for measuring the channel quality and demodulating received data symbols. A UE may measure a channel by the CRS so as to support the UE to perform cell reselection and switch to a target cell. In the LTE R10, two reference signals, i.e., channel state information reference signal (CSI-RS) and demodulation reference signal (DMRS), are respectively designed for further improving the average spectrum efficiency and cell edge spectrum efficiency of a cell and the throughput rate of each UE, wherein CSI-RS is used for measuring a channel, DMRS is used for demodulating a downlink shared channel. The demodulation using DMRS may reduce the interference between different receiving sides and between different cells by a beam method, reduce the performance degradation caused by codebook granularity, and reduce the cost of downlink control signalling to some extent.
In a heterogeneous network, since there is strong interference among different types of base stations, and considering the interference of a macro eNodeB on a Pico eNodeB and the interference of a Home eNodeB on a Macro eNodeB, LTE R11 provides a method of multiple antenna transmission based on user-dedicated pilot frequency to solve the problem of interference; in addition, the coordination of the inter-cell interference in the frequency domain may be implemented by mapping PDCCH to a PDSCH region in a frequency division multiplexing mode similar to PDSCH multiplexing mode. Such enhanced PDCCH is referred to as enhanced PDCCH (ePDCCH). At present, ePDCCH mapping methods mainly include continuous mapping and discrete mapping. In addition, one resource block pair may carry 2, 3 or 4 ePDCCHs, and one resource block pair uses one or more of antenna ports {107, 108, 109, 110}, as shown in FIG. 2. In addition, a search space of the enhanced Physical Downlink Control Channel of UE also includes a UE-specific search space.
As to the problem of poor ePDCCH transmission performance caused by the ePDCCH processing method in the related art, no effective solution has been proposed at present.